Existence of heme oxygenase-carbon monoxide-cyclic guanosine monophosphate pathway in human trabecular meshwork cells in vitro

HES1 promotes extracellular matrix protein expression and inhibits proliferation and migration in human trabecular meshwork cells under oxidative stress

Glaucoma is the leading cause of irreversible blindness. The most prevalent form of glaucoma is primary open-angle glaucoma (POAG). Oxidative stress is one of the major pathogenic factors of the POAG, and can elicit molecular and functional changes in trabecular meshwork cells, causing increased aqueous humor outflow resistance and elevated intraocular pressure. However, the regulatory mechanisms underlying oxidative stress-induced cell phenotypic changes remain elusive. Herein, we exposed primary human trabecular meshwork cells to the oxidative stress induced by 300 μM H₂O₂ for 2 h, and found significantly up-regulated expression of extracellular matrix proteins and a transcription factor, hairy and enhancer of split-1 (HES1). The cell functions, including migration and proliferation, were impaired by the oxidative stress. Furthermore, HES1 shRNA abrogated the extracellular matrix protein up-regulation and rescued the functional defects caused by the oxidative stress; conversely, HES1 overexpression resulted in the molecular and functional changes similar to those induced by H₂O₂. These results suggest that HES1 promotes extracellular matrix protein expression and inhibits proliferative and migratory functions in the trabecular meshwork cells under oxidative stress, thereby providing a novel pathogenic mechanism underlying and a potential therapeutic target to the POAG.

Heme oxygenase and ocular disease: a review of the literature

Heme oxygenase (HO) catabolizes heme into three products: carbon monoxide (CO), biliverdin/bilirubin and free iron. Two distinct isoforms of HO have been identified: an inducible isozyme HO-1 and a constitutively expressed isozyme HO-2, which participate in a variety of physiological and pathophysiological processes. A growing body of evidence indicates that HO activation plays a variety of roles in several ocular diseases, functioning protectively by reducing oxidative injury, attenuating the inflammatory response, and inhibiting cell apoptosis. This review focuses on the current understanding of the physiological significance of HO and its putative roles in the ocular disease. Possible therapeutic strategies involving HO in the treatment of ocular disease are discussed.